Screening device comprising a sieve deck capable of turning on a shaft



Oct. 3, 1967 J. N. 1. LEEMAN 3,344,919

SCREENING DEVICE COMPRISING A SIEVE DECK CAPABLE OF TURNING ON A SHAFT Filed Feb. l2, 1965 2 Sheets-Sheet l Filed Feb. l2, 1965 Oct. 3, 1967 J N. J. I EEMAN 3,344,919

SCREENING DEVICE COMPRISING A SIEVE DECK CAPABLE OF' TURNING ON A SHAFT 2 Sheets-Sheet 2 FIG. 2

United States Patent C) 3,344,919 SCREENING DEVICE COMPRISING A SIEVE DECK CAPABLE F TURNING 0N A SHAFT Jan N. J. Leeman, Heerlen, Netherlands, assigner to Stamicarbon NN., Heerlen, Netherlands Filed Feb. 12, 1965, Ser. N0. 432,356 Claims priority, application Netherlands, Feb. 19, 1964, 64-1,500 5 Claims. (Cl. 209-251) The present invention relates to improvements in screening devices of the sieve bend type, and more particularly to improvements in the rotatable mounting of sieve bends.

Sieve bend installations are known in the art, such as in U.S. Letters Patent No. 2,748,941 dated lune 5, 1956; N-o. 2,814,388 dated Nov. 26, 1957; and No. 2,916,142 dated Dec. 8, 1959, and pertinent subject matter thereof relating to sieve bend theory and operation is incorporated herein by reference, such that a more detailed explanation is unnecessary.

Typic-al rotatably mounted screening devices of the type relating to the present invention are those comprising supply means, discharge means, and a sieve bend extending therebetween and installed in a holder or housing mounted on a shaft whose center line coincides with the axis `of symmetry of the sieve bend. The shaft is rotatably tted in a structure capable of tilting from an operative position into a position in which the holder can be swung or rotated on the shaft. A screening device of this type is described in United States Letters Patent No. 3,007,574 to DeKoning, dated Nov. 7, 1961, and the subject matter thereof is incorporated herein by reference.

In this known device, the supporting member consists of an arm capable of turning at one end on a rigidly supported horizontal shaft, the arrangement being such that the holder, together with the sieve bend, can be tilted on the horizontal shaft and thus be moved into a position in which it can be swung on the central shaft without the sieve bend getting into contact with the supply and discharge means. In the device of Patent No. 3,007,574, the horizontal shaft is preferably arranged at a lower level than the central shaft, and a supporting member is provided on which the arm can rest after pivoting on the horizontal shaft, the latter shaft being so placed that, when the sieve bend is in the one extreme position, its center of gravity is on that side of the vertical plane through the horizontal shaft where the supporting member is provided, while it is on the other side of such plane when the sieve bend is in the other eX- treme position. Consequently, when the sieve bend is pivoted on the horizontal shaft, its center of gravity will travel along the upper part of its circle of rotation, so that it will move along the substantially horizontal line. The result will be that the power consumption or force required for tilting the `sieve bend is reduced to a minimum. The same applies to the power or force needed for restoring the sieve bend to its operative position.

This known device gives good service, but, if the sieve bend is made larger and, hence, heavier, a correspondingly larger initial moment of force will have to be exerted to overcome the moment of inertia and tilt the sieve bend. During tilting, 4the moment to be overcome decreases, equalling zero when the center of gravity of the sieve bend has arrived over the tilting shaft, and, after that, the moment to be overcome increases again. The latter increase involves overcoming the kinetic energy of the moving sieve bend which must be overcome to prevent severe impact between the sieve bend and the supporting member. Strong impact between the sieve bend and the supporting apparatus is desirably prevented as "ice it could result in serious damage and warping of the entire apparatus. Consequently, if the size and the weight of the sieve bend of the device according to Patent No. 3,007,574 are increased, more than one operator will be needed for tilting th seieve bend Iand for exerting and checking the various forces.

It is therefore the principal object of the presen-t invention to provide Va screening device with improved supporting means to permit easy manual movement thereof, even when heavy sieve bends are employed.

Other and further objects of 4this invention, together with an appreciation for the advantages thereof, will become increasingly apparent as this description proceeds.

Broadly stated, the objects of this invention are achieved, and advantages realized, by providing a screening device such as a sieve bend with an improved supporting structure comprising a curved member enabling the screening device to tilt and roll `over a supporting surface, the arrangement being such that, during tilting of the screening device or sieve bend, the center of gravity of the tiltable parts of the screening device will, in every position of the tiltable parts, be in or close to a vertical plane passing through the line of contact between the surface of the curved member and the supporting surface, and such that the center of gravity of the tiltable parts will remain in a substantially horizontal plane. This mode of construction ensures that the center of gravity will always remain over the fulcrum point so that, neglecting the rolling friction, the force required to exert the tilting moment will always be practically nil. The curved member and the supporting member may comprise one member each or may consist of a plurality of such members co-acting in pairs. Preferably, the curved surface will form part of the surface of a body of revolution having an axis which is horizontal and runs through the center of gravity of the tiltable parts of the screening device. If the curved surface forms part of a circular cylinder, the supporting surface will be a horizontal plane.

Preferably, means are also provided for preventing the tiltable parts of the screening device from sliding over the supporting member, to thereby ensure that the tiltable parts will be restored exactly to the original position.

The invention will be better understood when reference is had to the accompanying drawings wherein an illustrative embodiment is shown and wherein:

FIGURLE 1 is a vertical side elevation, partly in section of a screening device according to the invention, the dashed lines indicating the inoperative position thereof; and

FIGURE 2 is a front elevation of the installation shown in FIGURE 1.

'Referringrnow to the drawings, there is shown an installation embodying the principles of the invention wherein the reference numeral 1 indicates a slot-shaped aperture through which the material to be treated can be fed tangentially to a sieve bend indicated by the reference numeral 2, the screening deck 3 of which consists, for instance, of horizontal screen bars separated by slots. These bars, which in FIGURE 2 are represented by horizontal lines, are disposed between two curved side plates 4. By means of a number of wedges 5, the screening deck 3 is held against supporting rods 6 provided under the deck. The sieve bend is disposed within a suitable housing or holder 7 comprising side plates 8, guide plates 9 for the oversize fraction, and a bottom 10. The bottom 10 is provided with openings 11 for discharging the undersize fraction of the sieve bend.

The holder 7 is supported on a shaft 12, which is provided under the bottom Wall 10. The center line of the shaft 12 coincides with the axis of symmetry of the sieve bend and, consequently, with a line bisecting the sector angle of the screening deck.

The shaft 12 is rotatably carried in at least one and preferably in two bearings 13. These bearings 13 are fastened to a tilting member 14. The underside of the tilting member 14 is provided with a curved surface defined by a curved plane comprising either a curved plate or a plurality of bar-like members 18 of circular curvature for supporting the tiltable parts of the screening device on one or a plurality of fixed support members 15. A single fiat member 15 may be employed with a single curved plane defining the underside of tilting member 14, or a plurality of both may be employed in the case of large sieve bends, as is best shown in FIGURE 2.

In FIGUR-E 1, the sieve bend is shown in the operative position. The tiltable parts can be rolled back over the support 15 into the position represented by the dashed lines in FIGURE 1, in which position the sieve bend, together with the holder, can be reversed or rotated through an arc of 180. When the sieve bend is in the operative position, the center of gravity Z of the tiltable parts is vertically disposed over a line defining the fulcrum point A. As the center of gravity lies on the axis of the circular cylinder comprising the two curved surfaces and the support is horizontal, the center of gravity will, during tilting, travel along a horizontal line until it has arrived at the point Z'. The point Z is located vertically over a line defining the fulcrum point A. During tilting it is only necessary to overcome frictional resistance because the center of gravity is always disposed over the fulcrum point, i.e., the point of contact between the curved surface and the surface of the support 15.

With the construction according to the invention, replacement of the screening deck is considerably simpler than with the known device according to the United States Letters Patent No. 3,007,574 owing to the fact that, if the screening device is in the position indicated by the broken line, the shaft 12 is perpendicular to the support 15 and the sieve bend does not tend to slide down when the wedges 5 are loosened. Moreover, both reversal and replacement are facilitated according to the present invention since greater movement of the tiltable parts is lobtainable and therefore, a greater separation will be had from the supply and discharge means than is obtainable in the known construction.

According to another feature of the present invention, the surface 15, which may be curved or flat and planar, may be provided with the teeth-like pins 17 which are adapted to be received within the openings 16 defined by spaces between the curved bars 18, or defined by circular openings in the case of a curved plane. Thus, during rolling or tilting of the device according to the invention, the pins 17 will coact with the openings 16.

It thus will be seen that the objects of this invention have been fully and effectively accomplished. It will -be realized, however, that the foregoing specific embodiment has been shown and described only for the purpose of illustrating the principles of this invention and is subject to extensive change without departure from such principles.

Therefore, this invention includes all modifications encompassed within the spirit and scope of the following claims.

What is claimed is:

1. In a screening apparatus comprising supply means, discharge means, a sieve deck extending therebetween, said sieve deck being mounted on a shaft having a center line coinciding with the axis of symmetry of the sieve deck and said shaft being rotatably mountedin a movable support structure capable of tilting from an operative position into a position wherein the sieve deck may be rotated on said shaft into reverse relationship with respect to the supply means and discharge means, the improvement wherein the movable support structure comprises a tilting member and a supporting surface, the tilting member having a curved bottom member adapted to roll over the supporting surface such that during tilting of the sieve deck, the combined center of gravity of the sieve deck, shaft and tilting member will lie substantially in a vertical plane passing through any line of contact between the curved member and the supporting surface, and such that said center of gravity will define a substantially horizontal line during tilting of the sieve deck.

2. The screening apparatus of claim 1 wherein the surface of the curved member in contact with the supporting surface lies in a curved plane comprising part of an imaginary circular cylinder having a horizontal axis running through said combined center of gravity and wherein the surface of the supporting surface in contact with the curved member lies in a horizontal plane.

3. A screening apparatus according to cliam 1 wherein the screening deck is curved along the line of flow followed by material discharging from the discharge means.

4. The screening apparatus of claim 1 wherein the supporting surface and curved member are provided with interengaging means preventing sliding movement therebetween during the tilting movement.

5. The screening apparatus of claim 4 wherein the interengaging means comprises a plurality of pins on the supporting surface, and a plurality of pin receiving openings inthe curved member.

References Cited UNITED STATES PATENTS 1,370,999 3/ 1921 Scherzer 14-39 2,035,193 3/1936 Russell 14-39 3,007,574 1 1/ 1961 Koning 209--251 OTHER REFERENCES Hool & Kinne, Movable and Long-Span Steel Bridges, second edition, McGraw-Hill, N.Y. 1943, pp. 15-17 relied on.

HARRY B. THORNTON, Primary Examiner.

FRANK W. LUTTER, TIM R. MILES, Examiners.

L. H. EATHERTON, Assistant Examiner. 

1. IN A SCREENING APPARATUS COMPRISNG SUPPLY MEANS DISCHARGE MEANS, A SIEVE DECK EXTENDING THEREBETWEEN, SAID SIEVE DECK BEING MOUNTED ON A SHAFT HAVING A CENTER LINE COINCIDING WITH THE AXIS OF SYMMETRY OF THE SIEVE DECK AND SAID SHAFT BEING ROTATABLY MOUNTED IN A MOVABLE SUPPORT STRUCTURE CAPABLE OF TILTING FROM AN OPERATIVE POSITION INTO A POSITION WHEREIN THE SIEVE DECK MAY BE ROTATED ON SAID SHAFT INTO REVERSE RELATIONSHIP WITH RESPECT TO THE SUPPLY MEANS AND DISCHARGE MEANS, THE IMPROVEMENT WHEREIN THE MOVABLE SUPPORT STRUCTURE COMPRISES A TILTING MEMBER AND A SUPPORTING SURFACE, THE TILTING 